Uticaj starenja stabilizovanog i solidifikovanog sedimenta na strukturne karakteristike matriksa i izluživanje metala

Abstract

Predmet izučavanja ove disertacije obuhvatio je ispitivanje uticaja starenja stabilizovanog/solidifikovanog (S/S) sedimenta zagađenog teškim metalima i arsenom, i efikasnost primenjenih imobilizacionih agenasa (Portland cement, kreč, leteći pepeo, zeolit, montmorilonit i kaolinit) nakon dugogodišnjeg starenja S/S smeša. Shodno tome ispitana je dugoročna stabilnost i postojanost dobijenih S/S smeša sa aspekta izluživanja pomenutih metala, promene u minerološkim i strukturnim karakteristikama, kao i uticaj sušenja i zrenja materijala na pomenute parametre. Istraživanja u disertaciji obuhvatila su dve faze. Prva faza imala je za cilj procenu rizika i početnu karakterizaciju netretiranog sedimenta primenom analize pseudo-ukupnog sadržaja metala kojom je utvrđen sadržaj metala u početnom uzorku sedimenta. Druga faza uključivala je primenu tretmana stabilizacije i solidifikacije na kontaminirani sediment dodavanjem različitih imobilizacionih agenasa. Analize su se vršile nakon 7 i 28 dana od primenjenog S/S tretmana, kao i nakon 7 godina sa ciljem da se utvrdi uticaj višegodišnjeg starenja i zrenja monolitnih smeša na mobilnost metala i strukturne karakteristike smeša. U okviru druge faze istraživanja ispitana je toksičnost S/S smeša primenom DIN i TCLP testova izluživanja, dok je test toksičnosti primenom bakterija Vibrio Fischeri doprineo u sagledavanju procene rizika S/S smeša po organizme. Nakon 28 dana i 7 godina korišćena je sekvencijalna ekstrakcija za određivanje mobilnost i biodostupnost metala u monolitnim matriksima. U cilju utvrđivanja mikrostukturnih karakteristika sedimenta primenjena je rendgenska difrakciona analiza (XRD) za ispitivanje kristalnih struktura S/S smeša i detekciju mineralnog sastava. Pomoću elektronskog mikroskopa i energodisperzivnog detektora sa X-zrakom (SEM/EDS) određena je kvalitativna i kvantitativna distribucija metala i drugih elemenata od interesa, dok se za identifikaciju formiranih funkcionalnih grupa u monolitnim smešama primenio spektrometar sa infracrvenom Furijeovom transformacijom (FTIR). Na osnovu dobijenih rezultata zaključeno je da se mobilnost teških metala i arsena značajno smanjila nakon 7 godina za smeše tretirane cementom (C5), krečom (L10), letećim pepelom (F30) i kaolinitom (K20), a efekat stabilizacije je pokazan transformacijom metala iz direktne toksične frakcije u stabilnije oblike. Smeše C5 i K20 ispoljavaju najmanje toksične efekate od svih smeša, jer je procenat inhibicije na bioluminiscentnim bakterijama manji od 13%, dok je u pogledu izdržljivosti monolitna smeša C5 pokazala najveću pritisnu čvrstoću od svih smeša. Dobijeni podaci su neprocenjivi za dobijanje stvarnog uvida u dugoročnu efikasnost primenjenog tretmana i mogućnost bezbedne upotrebe ili odlaganja dobijenih S/S smeša sa aspekta zaštite životne sredine, kao i ekonomski i ekološki prihvatljivog upravljanja opasnim otpadom.

The subject of study in this dissertation included to investigate the effect of aging of stabilized/solidified (S/S) sediment contaminated with heavy metals and arsenic, and the efficacy of the applied immobilization agent (Portland cement, lime, fly ash, zeolite, montmorillonite and kaolinite) after long-term aging of S/S mixtures. The long - term stability and stability of the obtained S/S mixtures from the aspect of leaching of the mentioned metals, changes in mineralogical and structural characteristics, as well as the influence of drying and maturation of the material on the mentioned parameters were examined. The research in the dissertation included two phases. The first phase aimed at risk assessment and initial characterization of untreated sediment using pseudo-total metal content analysis which determined the metal content in the initial sediment sample. The second phase involved applying stabilization and solidification treatments to the contaminated sediment by adding various immobilizing agents. The analyzes were performed after 7 and 28 days from the applied S/S treatment, as well as after 7 years in order to determine the influence of perennial aging and maturation of monolithic mixtures on metal mobility and structural characteristics of the mixtures. In the second phase of the study, the toxicity of S/S mixtures using DIN and TCLP leaching tests was examined, while the toxicity test using bacteria Vibrio Fischeri contributed to the assessment of the risk of S/S mixtures to organisms. After 28 days and 7 years, sequential extraction was used to determine the mobility and bioavailability of metals in monolithic matrices. In order to determine the microstructural characteristics of the sediment, x-ray diffraction analysis (XRD) was used to examine the crystal structures of S/S mixtures and to detect the mineral composition. The qualitative and quantitative distribution of metals and other elements of interest was determined using an electron microscope and an energy-dispersive X-ray detector (SEM / EDS), while an infrared Fourier transform spectrometer(FTIR) was used to identify the formed functional groups in monolithic mixtures. Based on the obtained results, it was concluded that the mobility of heavy metals and arsenic decreased significantly after 7 years for mixtures treated with cement (C5), lime (L10), fly ash (F30) and kaolinite (K20), and the stabilization effect was shown by transformation of metals from direct toxic fractions into more stable forms. Mixtures C5 and K20 exhibit the least toxic effects of all mixtures, because the percentage of inhibition on bioluminescent bacteria is less than 13%, while in terms of durability, the monolithic mixture C5 showed the highest compressive strength of all mixtures. The obtained data are invaluable for gaining real insight into the long-term efficiency of the applied treatment and the possibility of safe use or disposal of the obtained S/S mixtures from the aspect of environmental protection, as well as economically and ecologically acceptable hazardous waste management.